The present invention relates to a steering apparatus which steers the steered wheels of a vehicle.
A steering system employing a steering wheel as a driving apparatus, which steers the steered wheels of a vehicle, has been known. The steering system converts the rotational motion of a steering wheel into the linear motion of a rack axis in a steering gearbox, thus driving a link mechanism connected to the rack axis to steer the steered wheels.
In recent years another steering apparatus with joysticks instead of a steering wheel to steer the steered wheels of a vehicle has been proposed. This type of driving apparatus is disclosed in the patent gazette Japanese Laid-Open Patent 9-301193 as a prior example. This driving apparatus has at least two joysticks (control knobs) and performs the acceleration/deceleration or the turning of a vehicle with the operation of the joysticks in the direction of forward, backward, rightward or leftward. For example, a vehicle is accelerated when a forward operational force is added to the respective joysticks or it is decelerated when a backward operational force is added to them. And, the steered wheels are turned to the right when a rightward force is added to the respective joysticks or they are turned to the left when a leftward force is added to the respective joysticks. The respective joysticks are functionally equivalent and a driver can select and operate only one joystick or operate a plurality of joysticks simultaneously. When a plurality of joysticks ire simultaneously operated, provision for the operational contradiction among joysticks is made by prioritizing each joystick and accepting the operation with a joystick in the order of priority. This type of driving apparatus is more advantageous than the prior driving apparatus with a steering wheel because the layout flexibility and reliability are improved and die access from the right or left seat is selectable with a plurality of joysticks.
However, this type of driving apparatus has had difficulty in giving a small correction to the steering amount, which is one of basic performances required for steering. The steering wheel is able to rotate (operate) more than two revolutions; on the other hand the joystick is only able to operate within the tilt amount (tilt displacement) in the direction of forward/backward or right/left. So it is necessary to make the steering amount per unit operational amount (angle) of joystick bigger than the steering amount per unit operational angle of a steering wheel, however in doing so a fine correction of steering amount was difficult since the steered wheels made a large steering with a small operational amount. All the joysticks disclosed in the patent gazette Japanese Laid-Open Patent 9-301193 are of the same function, namely of the same characteristics. Therefore, it was difficult to give a fine correction to the steering amount, which had been realized by the steering wheel, since the operation was actually equivalent with one joystick operation even if selection or prioritization was made.
Further, the driving apparatus had problems that it required a complex control device for switching the respective joysticks or prioritizing them when a plurality of joysticks was in operation simultaneously, and confirmation by a driver of the switching operation or the operable joystick.
Therefore, the object of the present invention is to provide a driving apparatus, which enables the improvement of operational performance of a vehicle in driving, by allowing a fine correction of steering amount with a simple structure when a steering of steered wheels is performed with an operation device composed of joysticks etc.
The present invention to address the above issues provides a driving apparatus for a vehicle, which has an operation device operated by a driver, and in which an operation amount monitoring unit equipped in the operation device detects the operation amount of the operation device and a control device controls the steered wheels of a vehicle with the detected value, wherein the operation device comprises a first and a second operation devices, the control device comprises a steering amount setting unit which determines the steering amount for the steered wheels based on the resultant of the first detected operation amount resulting from the operation of the first operation device and the second detected operation amount resulting from the operation of the second operation device, and a first steering gain which is a ratio of the steering amount of steered wheels to the operation amount of the first operation device and a second steering gain which is a ratio of the steering amount of the steered wheels to the operation amount of the second operation device are differentiated.
The driving apparatus thus structured is capable of differentiating the steering amount per unit operation amount of the first and the second operation devices by setting the first and the second steering wheel gains different, as well as making the respective first and second operation devices contribute to the setting of the steering wheel amount. For example, in the case the gain of the second operation device is lower than that of the first operation device, it will be possible to utilize the second operation device as a fine adjustment means for the first operation device, since it can be set so that the steering amount per unit operation amount of the second operation device is less than that of the first operation device. Therefore, it will promote the operational performance of a vehicle as well as the improvement of the accuracy of steering wheel angle.